This invention is directed to an improvement to a cyanoethylation process. The process involved can be continuous or batch. Cyanoethylation refers to the reaction between acrylonitrile and a variety of compounds to yield .beta.-substituted propionitrile derivatives. The compounds are characterized by their possession of a labile hydrogen atom. The latter is a hydrogen atom bonded to an electronegative substituent. Classes of compounds containing labile hydrogen atoms include those having hydroxyl groups, e.g., polyhydric alcohols. Cyanoethylation can be generalized by the following reaction formula: EQU CH.sub.2 .dbd.CHCN+RH.revreaction.RCH.sub.2 CH.sub.2 CN
for polyhydric alcohols the general reaction formulas are as follows: EQU CH.sub.2 .dbd.CHCN+HOROH.revreaction.CNCH.sub.2 CH.sub.2 OROH EQU ch.sub.2 chcn+cnch.sub.2 ch.sub.2 oroh.revreaction.cnch.sub.2 ch.sub.2 oroch.sub.2 ch.sub.2 cn
cyanoethylation products are useful intermediates for the manufacture of plastics and fibers.
Cyanoethylation is used in the formation of a great variety of polyfunctional nitriles, for example see Encyclopedia of Chemical Technology, Kirk-Othmer, 2nd Edition, Volume 6, and Organic Reactions, R. Adams et al, Vol. 5, John Wiley and Sons, N.Y. 1949. Cyanoethylation using ion exchange resin catalyst is disclosed in J. of Org. Chem., Vol. 27, May 1962, pages 1920-1921, "Catalysis by Ion Exchange Resins. Improved Cyanoethylation and Carbamylethylation of Diols."
The cyanoethylation reaction has a tendency to be accompanied by polymerization of the acrylonitrile. It is desirable to avoid the polymerization side reaction since valuable starting material is converted to less valuable by-products. Techniques suggested to minimize the unwanted polymerization include maintaining a lower temperature by cooling the exothermic reaction, diluting the reaction mixture with an inert solvent, use of soluble or highly dispersed catalyst and the gradual addition of acrylonitrile with mechanical mixing. However, the aforementioned solutions suffered from various shortcomings such as additional capital expenditures, and/or additional materials handling costs, and/or additional separation steps and costs.
Overcoming the aforementioned problem of an unwanted side reaction and avoiding the shortcomings of the aforementioned solutions is the present invention which is an improvement to the cyanoethylation process. The improvement results in a high yield of the desired cyanoethylation product, for example 3,3'-ethylene dioxybis(propionitrile) from the reaction between ethylene glycol and acrylonitrile. In other words the amount of acrylonitrile polymer formed is minimized. Further when certain reactants are used, as disclosed hereinafter, a product intermediate can be recycled and serves as a solvent and facilitates the reaction. Still further the resulting cyanoethylated product stream is of rather high purity which simplifies subsequent processing.